He takes out his keys and unscrews the outlet cover to remove the ricin.

The poison that Walt made towards the end of Season 1, but still has never used it heading into the season finale. He almost used it on Tuco and Gus, and pretended to use it on Brock, but it has never actually been used yet. It will either play a huge part in the finale (Chekov’s gun), or it will continue to be the red herring it has been all along.